U.S. patent application number 12/715243 was filed with the patent office on 2010-09-02 for tiled substrates for deposition and epitaxial lift off processes.
This patent application is currently assigned to ALTA DEVICES, INC.. Invention is credited to Gang He, Andreas Hegedus.
Application Number | 20100219509 12/715243 |
Document ID | / |
Family ID | 42666272 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100219509 |
Kind Code |
A1 |
He; Gang ; et al. |
September 2, 2010 |
TILED SUBSTRATES FOR DEPOSITION AND EPITAXIAL LIFT OFF
PROCESSES
Abstract
Embodiments of the invention generally relate to epitaxial lift
off (ELO) films and methods for producing such films. Embodiments
provide a method to simultaneously and separately grow a plurality
of ELO films or stacks on a common support substrate which is tiled
with numerous epitaxial growth substrates or surfaces. Thereafter,
the ELO films are removed from the epitaxial growth substrates by
an etching step during an ELO process. The tiled growth substrate
contains the epitaxial growth substrates disposed on the support
substrate may be reused to grow further ELO films. In one
embodiment, a tiled growth substrate is provided which includes two
or more gallium arsenide growth substrates separately disposed on a
support substrate having a coefficient of thermal expansion within
a range from about 5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1.
Inventors: |
He; Gang; (Sunnyvale,
CA) ; Hegedus; Andreas; (Burlingame, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, L.L.P.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
ALTA DEVICES, INC.
Santa Clara
CA
|
Family ID: |
42666272 |
Appl. No.: |
12/715243 |
Filed: |
March 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61156404 |
Feb 27, 2009 |
|
|
|
Current U.S.
Class: |
257/618 ;
257/E21.09; 257/E29.089; 438/478 |
Current CPC
Class: |
H01L 21/02395 20130101;
C30B 25/18 20130101; H01L 31/184 20130101; Y02E 10/544 20130101;
H01L 31/1844 20130101; H01L 21/6835 20130101; H01L 2221/6835
20130101; H01L 21/02463 20130101; H01L 21/02425 20130101; H01L
31/03046 20130101; H01L 31/0735 20130101; C30B 29/42 20130101 |
Class at
Publication: |
257/618 ;
438/478; 257/E29.089; 257/E21.09 |
International
Class: |
H01L 29/20 20060101
H01L029/20; H01L 21/20 20060101 H01L021/20 |
Claims
1. A gallium arsenide substrate assembly, comprising: a support
substrate comprising a coefficient of thermal expansion within a
range from about 5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1; an adhesion layer disposed on
the support substrate; and at least two gallium arsenide growth
substrates separately disposed on the adhesion layer and next to
each other, wherein a gap extends between and separates the gallium
arsenide growth substrates from each other.
2. The gallium arsenide substrate assembly of claim 1, wherein the
coefficient of thermal expansion is within a range from about
5.2.times.10.sup.-6.degree. C..sup.-1 to about
8.5.times.10.sup.-6.degree. C..sup.-1.
3. The gallium arsenide substrate assembly of claim 1, wherein the
at least two gallium arsenide growth substrates comprise 4 or more
gallium arsenide growth substrates.
4. The gallium arsenide substrate assembly of claim 3, wherein the
at least two gallium arsenide growth substrates comprise 12 or more
gallium arsenide growth substrates.
5. The gallium arsenide substrate assembly of claim 1, wherein the
support substrate comprises a material selected from the group
consisting of niobium, niobium alloys, titanium carbide, magnesium
silicate, steatite, tungsten carbide, tungsten carbide cermet,
iridium, alumina, alumina ceramics, zirconium, zirconium alloys,
zirconia, zirconium carbide, osmium, tantalum, hafnium, molybdenum,
molybdenum alloys, oxides thereof, silicates thereof, alloys
thereof, derivatives thereof, and combinations thereof.
6. The gallium arsenide substrate assembly of claim 1, wherein the
support substrate has no porosity or substantially no porosity.
7. The gallium arsenide substrate assembly of claim 1, wherein the
support substrate is resistant or substantially resistant to
hydrogen fluoride or hydrofluoric acid.
8. The gallium arsenide substrate assembly of claim 1, wherein the
adhesion layer comprises an optical adhesive or a UV-curable
adhesive.
9. The gallium arsenide substrate assembly of claim 8, wherein the
adhesion layer comprises a mercapto ester compound.
10. The gallium arsenide substrate assembly of claim 9, wherein the
adhesion layer further comprises a material selected from the group
consisting of butyl octyl phthalate, tetrahydrofurfuryl
methacrylate, acrylate monomer, derivatives thereof, and
combinations thereof.
11. The gallium arsenide substrate assembly of claim 1, wherein the
adhesion layer comprises silicone or sodium silicate.
12. A gallium arsenide substrate assembly, comprising: an adhesion
layer disposed on a support substrate; and at least two gallium
arsenide growth substrates separately disposed on the adhesion
layer and next to each other, wherein the support substrate
comprises a coefficient of thermal expansion for providing a
maximum strain of about 0.1% or less within the gallium arsenide
growth substrates at a temperature of about 650.degree. C. or less,
and a gap extends between and separates the gallium arsenide growth
substrates from each other.
13. The gallium arsenide substrate assembly claims 12, wherein the
coefficient of thermal expansion is about 9.times.10.sup.-6.degree.
C..sup.-1 or less.
14. The gallium arsenide substrate assembly of claim 13, wherein
the coefficient of thermal expansion is within a range from about
5.times.10.sup.-6.degree. C..sup.-1 to about
8.times.10.sup.-6.degree. C..sup.-1.
15. The gallium arsenide substrate assembly of claim 12, wherein
the coefficient of thermal expansion is within a range from about
5.2.times.10.sup.-6.degree. C..sup.-1 to about
8.5.times.10.sup.-6.degree. C..sup.-1.
16. The gallium arsenide substrate assembly of claim 12, wherein
the at least two gallium arsenide growth substrates comprise 4 or
more gallium arsenide growth substrates.
17. The gallium arsenide substrate assembly of claim 16, wherein
the at least two gallium arsenide growth substrates comprise 12 or
more gallium arsenide growth substrates.
18. The gallium arsenide substrate assembly of claim 12, wherein
the support substrate comprises a material selected from the group
consisting of niobium, niobium alloys, titanium carbide, magnesium
silicate, steatite, tungsten carbide, tungsten carbide cermet,
iridium, alumina, alumina ceramics, zirconium, zirconium alloys,
zirconia, zirconium carbide, osmium, tantalum, hafnium, molybdenum,
molybdenum alloys, oxides thereof, silicates thereof, alloys
thereof, derivatives thereof, and combinations thereof.
19. The gallium arsenide substrate assembly of claim 12, wherein
the support substrate has no porosity or substantially no
porosity.
20. The gallium arsenide substrate assembly of claim 12, wherein
the support substrate is resistant or substantially resistant to
hydrogen fluoride or hydrofluoric acid.
21. The gallium arsenide substrate assembly of claim 12, wherein
the adhesion layer comprises an optical adhesive or a UV-curable
adhesive.
22. The gallium arsenide substrate assembly of claim 21, wherein
the adhesion layer comprises a mercapto ester compound.
23. The gallium arsenide substrate assembly of claim 22, wherein
the adhesion layer further comprises a material selected from the
group consisting of butyl octyl phthalate, tetrahydrofurfuryl
methacrylate, acrylate monomer, derivatives thereof, and
combinations thereof.
24. The gallium arsenide substrate assembly of claim 12, wherein
the adhesion layer comprises silicone or sodium silicate.
25. A method for forming a tiled growth substrate, comprising:
forming an epitaxial material comprising gallium arsenide on a
sacrificial layer disposed on a host substrate; etching the
sacrificial layer while removing the epitaxial material from the
host substrate to form a gallium arsenide growth substrate during
an epitaxial lift off process; adhering at least two gallium
arsenide growth substrates on a support substrate; and exposing the
gallium arsenide growth substrates disposed on the support
substrate to additional deposition and epitaxial lift off
processes.
26. The method of claim 25, wherein the support substrate comprises
a coefficient of thermal expansion within a range from about
5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1.
27. The method of claim 26, wherein the coefficient of thermal
expansion is within a range from about 5.2.times.10.sup.-6.degree.
C..sup.-1 to about 8.5.times.10.sup.-6.degree. C..sup.-1.
28. The method of claim 25, wherein the support substrate comprises
a material selected from the group consisting of niobium, niobium
alloys, titanium carbide, magnesium silicate, steatite, tungsten
carbide, tungsten carbide cermet, iridium, alumina, alumina
ceramics, zirconium, zirconium alloys, zirconia, zirconium carbide,
osmium, tantalum, hafnium, molybdenum, molybdenum alloys, oxides
thereof, silicates thereof, alloys thereof, derivatives thereof,
and combinations thereof.
29. The method of claim 25, wherein the support substrate has no
porosity or substantially no porosity.
30. The method of claim 25, wherein the support substrate is
resistant or substantially resistant to hydrogen fluoride or
hydrofluoric acid.
31. The method of claim 25, further comprising forming an adhesion
layer on the support substrate and disposing the gallium arsenide
growth substrates on the adhesion layer.
32. The method of claim 31, wherein the adhesion layer comprises an
optical adhesive or a UV-curable adhesive.
33. The method of claim 32, wherein the adhesion layer comprises a
mercapto ester compound.
34. The method of claim 33, wherein the adhesion layer further
comprises a material selected from the group consisting of butyl
octyl phthalate, tetrahydrofurfuryl methacrylate, acrylate monomer,
derivatives thereof, and combinations thereof.
35. The method of claim 31, wherein the adhesion layer comprises
silicone or sodium silicate.
36. The method of claim 25, wherein the gallium arsenide growth
substrates comprise gallium arsenide alloys or derivatives
thereof.
37. The method of claim 25, wherein the support substrate comprises
4 or more gallium arsenide growth substrates.
38. The method of claim 37, wherein the support substrate comprises
12 or more gallium arsenide growth substrates.
39. The method of claim 25, wherein the epitaxial material
comprises a material selected from the group consisting of gallium
arsenide, aluminum gallium arsenide, indium gallium phosphide,
alloys thereof, derivatives thereof, and combinations thereof.
40. The method of claim 39, wherein the epitaxial material
comprises a layer comprising gallium arsenide and another layer
comprising aluminum gallium arsenide.
41. The method of claim 39, wherein the epitaxial material
comprises a gallium arsenide buffer layer, at least one aluminum
gallium arsenide passivation layer, and a gallium arsenide active
layer.
42. The method of claim 41, wherein the gallium arsenide buffer
layer has a thickness within a range from about 100 nm to about 500
nm, each of the aluminum gallium arsenide passivation layers has a
thickness within a range from about 10 nm to about 50 nm, and the
gallium arsenide active layer has a thickness within a range from
about 500 nm to about 2,000 nm.
43. The method of claim 39, wherein the epitaxial material
comprises a photovoltaic cell structure comprising multiple layers,
and the photovoltaic cell structure comprises at least two
materials selected from the group consisting of gallium arsenide,
n-doped gallium arsenide, p-doped gallium arsenide, aluminum
gallium arsenide, n-doped aluminum gallium arsenide, p-doped
aluminum gallium arsenide, indium gallium phosphide, alloys
thereof, derivatives thereof, and combinations thereof.
44. The method of claim 25, wherein the sacrificial layer comprises
a material selected from the group consisting of aluminum arsenide,
alloys thereof, derivatives thereof, and combinations thereof.
45. The method of claim 44, wherein the sacrificial layer comprises
an aluminum arsenide layer having a thickness within a range from
about 1 nm to about 20 nm.
46. A method for forming a tiled growth substrate, comprising:
forming a plurality of gallium arsenide growth substrates during
epitaxial lift off processes; adhering the plurality of gallium
arsenide growth substrates on a support substrate; and performing
deposition processes and additional epitaxial lift off processes to
the plurality of gallium arsenide growth substrates disposed on the
support substrate.
47. The method of claim 46, wherein the support substrate comprises
a coefficient of thermal expansion within a range from about
5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1.
48. A method for forming multiple epitaxial thin films during an
epitaxial lift off process, comprising: depositing a plurality of
aluminum arsenide sacrificial layers simultaneously on a plurality
of gallium arsenide growth surfaces disposed on a support
substrate, wherein a single aluminum arsenide sacrificial layer is
deposited on each gallium arsenide growth surface, and each of the
gallium arsenide growth surfaces is separately disposed on the
support substrate, next to each other, and a gap extends between
and separates the gallium arsenide growth surfaces from each other;
depositing a plurality of buffer layers simultaneously on the
plurality of aluminum arsenide sacrificial layers, wherein a single
buffer layer is deposited on each aluminum arsenide sacrificial
layer; depositing a plurality of gallium arsenide active layers
simultaneously on the plurality of buffer layers, wherein a single
gallium arsenide active layer is deposited on each buffer layer;
and etching the aluminum arsenide sacrificial layers while
separating the gallium arsenide active layers from the gallium
arsenide growth surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of U.S. Ser. No. 61/156,404,
filed Feb. 27, 2009, which is hereby incorporated by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to methods for
the fabrication of photovoltaic, semiconductor, and electronic
materials and devices, and more particularly relate to epitaxial
lift off (ELO) processes and the thin films and devices formed by
these process.
[0004] 2. Description of the Related Art
[0005] Photovoltaic or solar devices, semiconductor devices, or
other electronic devices are usually manufactured by utilizing a
variety of fabrication processes to manipulate the surface of a
substrate. These fabrication processes may include deposition,
annealing, etching, doping, oxidation, nitridation, and many other
processes. Generally, the manufactured devices generally
incorporate a portion or the whole base substrate into the final
architecture of the electronic device. For example, a photovoltaic
device is often formed on a gallium arsenide wafer which is
incorporated as an intimate part of the final photovoltaic device.
Epitaxial lift off (ELO) is a less common technique for fabricating
thin film devices and materials which does not incorporate the base
substrate into the final manufactured devices.
[0006] The ELO process provides growing an epitaxial layer, film,
or material on a sacrificial layer which is disposed on a growth
substrate, such as a gallium arsenide wafer. Subsequently, the
sacrificial layer is selectively etched away in a wet acid bath,
while the epitaxial material is separated from the growth
substrate. The isolated epitaxial material is a thin layer or film
and is usually referred to as the ELO film or the epitaxial film.
Each ELO film generally contains numerous layers of varying
compositions relative to the specific device, such as photovoltaic
or solar devices, semiconductor devices, or other electronic
devices.
[0007] The growth substrates are usually crystalline wafers of
gallium arsenide or other Group III/V elements. The growth
substrates are very fragile and expensive. The growth substrates
are so expensive as to be commercially cost prohibiting if
incorporated into the finished ELO film or device. Therefore, once
the ELO film has been removed, the growth substrates are cleaned,
treated, and reused to manufacture additional ELO films. While
reusing the growth substrates reduces some cost, the process of
refurbishing a growth substrate for each fabricated ELO film is
still quite expensive. The growth substrates must be refurbished
even if the ELO process does not yield a commercially viable ELO
film. Also, since the growth substrates are quite fragile, the
likelihood of chipping, cracking, or breaking a substrate increases
with each additional step exposed to the growth substrate during
the ELO or refurbishing processes. Furthermore, each of the growth
substrates has a finite life expectancy even if the substrate is
not damaged during the fabrication processes.
[0008] While the expense of growth substrates may be one factor
which has contributed to the lack of commercial utilization of the
ELO process, other factors have also plagued the use of this
technique. The overall ELO process has always been a cost
prohibiting technique for commercially producing the thin ELO film
devices. The throughput is quite low since current ELO processes
provide transferring a single growth substrate through many
fabrication steps while producing a single ELO film. The current
ELO processes are time consuming, costly, and rarely produce
commercial quality ELO films.
[0009] Therefore, there is a need for a method for growing
epitaxial film stacks by ELO processes, and a need for the method
to have a high throughput and to be more effective, less time
consuming, and less expensive than currently known ELO
processes.
SUMMARY OF THE INVENTION
[0010] Embodiments of the invention generally relate to epitaxial
lift off (ELO) films and methods for producing such films.
Embodiments provide a method to simultaneously and separately grow
a plurality of ELO films or stacks on a common support substrate
which is tiled with numerous epitaxial growth substrates (e.g.,
epitaxial or crystalline substrates, wafers, or surfaces).
Thereafter, the ELO films are removed from the epitaxial growth
substrates by an etching step during an ELO process. The overall
throughput is quite high since multiple ELO films may be
manufactured while exposing each tiled growth substrate to the
numerous fabrication processes, similar to a bulk process. However,
multiple tiled growth substrates, each containing a plurality of
epitaxial growth substrates disposed on a support substrate, may be
exposed consecutively or simultaneously to the fabrication
processes. The tiled growth substrate containing the epitaxial
growth substrates disposed on the support substrate may be reused
to grow further ELO films.
[0011] Each of the ELO films contains multiple epitaxial layers
which are grown by chemical vapor deposition (CVD) on a sacrificial
layer disposed on or over each epitaxial growth substrate. A
support film, handle, or tape may be disposed on or over the
opposite side of the ELO film as the support substrate. The support
film is used to stabilize the ELO films by maintaining compression
and to hold the ELO films during the etching and removal steps of
the ELO process, and thereafter.
[0012] The epitaxial growth substrates are a crystalline material
usually of a Group III/V compound, such as gallium arsenide. The
epitaxial growth substrates and the support substrate are generally
matched to have a similar or substantially similar coefficient of
thermal expansion (CTE) in order to reduce or prevent stress within
the epitaxial growth substrates, as well as the ELO films deposited
on the epitaxial growth substrates. Gallium arsenide, such as a
gallium arsenide growth substrate, usually has a CTE within a range
from about 5.73.times.10.sup.-6.degree. C..sup.-1 to about
6.86.times.10.sup.-6.degree. C..sup.-1. Therefore, in one
embodiment, a tiled growth substrate, such as a gallium arsenide
tiled growth substrate, is provided which includes a support
substrate and two or more gallium arsenide growth substrates
disposed over the support substrate, next to each other, and
detached from each other. The CTE of the support substrate may be
about 9.times.10.sup.-6.degree. C..sup.-1 or less, such as within a
range from about 5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1, preferably, from about
5.2.times.10.sup.-6.degree. C..sup.-1 to about
8.5.times.10.sup.-6.degree. C..sup.-1, and more preferably, from
about 5.26.times.10.sup.-6.degree. C..sup.-1 to about
8.46.times.10.sup.-6.degree. C..sup.-1.
[0013] In another embodiment, the tiled growth substrate is
provided which includes two or more gallium arsenide substrates are
separately disposed over a support substrate, wherein the support
substrate has a CTE for providing a maximum strain of about 0.1% or
less within the gallium arsenide substrates at a temperature of
about 650.degree. C. or less.
[0014] In order to achieve the same, similar, or substantially
similar coefficients of thermal expansion (CTEs) between the
epitaxial growth substrates and the support substrate, the types of
material in which the support substrate is chosen, in part, to
match or substantially match the CTE of the material contain within
the epitaxial growth substrates. Therefore, in many examples
described herein, the epitaxial growth substrates are wafers,
layers, thin films, or surfaces which contain epitaxial grown
gallium arsenide, gallium arsenide alloys, or derivatives thereof
and the support substrate contains or is made from at least one
metal or metallic material, ceramic material, or combinations
thereof.
[0015] In some examples, the support substrate may contain niobium,
niobium alloys, titanium carbide, magnesium silicate, steatite,
tungsten carbide, tungsten carbide cermet, iridium, alumina,
alumina ceramics, zirconium, zirconium alloys, zirconia, zirconium
carbide, osmium, tantalum, hafnium, molybdenum, molybdenum alloys,
chromium, oxides thereof, silicates thereof, alloys thereof,
derivatives thereof, or combinations thereof. In some examples, the
support substrate has no porosity or substantially no porosity. In
other examples, the support substrate may be resistant to hydrogen
fluoride and hydrofluoric acid.
[0016] In some embodiments, the tiled growth substrate may have
gaps extending between and separating the gallium arsenide
substrates from each other. In another embodiment, the tiled growth
substrate may have an adhesion layer disposed on the support
substrate, and two or more gallium arsenide substrates disposed on
the adhesion layer, next to each other, and detached from each
other. In another embodiment, the tiled growth substrate may have
the gaps between the gallium arsenide substrates and the adhesion
layer disposed between the support substrate and the gallium
arsenide substrates. The support substrate contains at least 2
epitaxial growth substrates, such as gallium arsenide substrates,
but usually contains 3, 4, 5, 6, 9, 12, 16, 20, 24, 50, 100, or
more epitaxial growth substrates or gallium arsenide
substrates.
[0017] In other embodiments, the adhesion layer contains a pressure
sensitive adhesive (PSA), an optical adhesive, or an
ultraviolet-curable adhesive. In some examples, the adhesion layer
may contain a mercapto ester compound and may further contain butyl
octyl phthalate, tetrahydrofurfuryl methacrylate, acrylate monomer,
derivatives thereof, or combinations thereof. In other examples,
the adhesion layer contains silicone or sodium silicate.
[0018] In another embodiment, a method for forming multiple
epitaxial thin films during an ELO process is provided which
includes depositing a plurality of aluminum arsenide sacrificial
layers simultaneously on a plurality of gallium arsenide growth
surfaces disposed on a support substrate, wherein a single aluminum
arsenide sacrificial layer is deposited on each gallium arsenide
growth surface, and each of the gallium arsenide growth surfaces is
separately disposed on the support substrate, next to each other,
and a gap extends between and separates the gallium arsenide growth
surfaces from each other. The method further includes depositing a
plurality of buffer layers simultaneously on the plurality of
aluminum arsenide sacrificial layers, wherein a single buffer layer
is deposited on each aluminum arsenide sacrificial layer,
depositing a plurality of gallium arsenide active layers
simultaneously on the plurality of buffer layers, wherein a single
gallium arsenide active layer is deposited on each buffer layer,
and etching the aluminum arsenide sacrificial layers while
separating the gallium arsenide active layers from the gallium
arsenide growth surfaces.
[0019] In another embodiment, a method for forming a tiled growth
substrate is provided which includes forming a plurality of
epitaxial growth substrates during ELO processes and adhering the
plurality of epitaxial growth substrates on a support substrate.
The method further includes depositing a sacrificial layer over
each epitaxial growth substrate disposed on the support substrate,
depositing epitaxial materials over each of the sacrificial layers,
and etching the sacrificial layers while removing the epitaxial
materials from the epitaxial growth substrates during an additional
ELO process. In other examples, the method provides exposing the
tiled growth substrate, that is, the epitaxial growth substrate
disposed on the support substrate, to additional deposition and ELO
processes in order to form a variety of ELO films and
materials.
[0020] In some examples, a method for forming a tiled growth
substrate is provided which includes forming a first sacrificial
layer on a host substrate, forming a first epitaxial layer over the
first sacrificial layer, etching the first sacrificial layer while
removing the first epitaxial layer from the host substrate and
forming a first epitaxial growth substrate during a first ELO
process, forming a second sacrificial layer on the host substrate,
forming a second epitaxial layer over the second sacrificial layer,
etching the second sacrificial layer while removing the second
epitaxial layer from the host substrate and forming a second
epitaxial growth substrate during a second ELO process, and
adhering the first and second epitaxial growth substrates on a
support substrate.
[0021] In various examples, the epitaxial material formed during
ELO processes descried herein may contain gallium arsenide,
aluminum gallium arsenide, indium gallium phosphide, alloys
thereof, derivatives thereof, or combinations thereof. The
epitaxial material may contain multiple layers. In one example, the
epitaxial material has a layer containing gallium arsenide and
another layer containing aluminum gallium arsenide. In one specific
example, the epitaxial material may have a cell structure of
multiple layers. The layers of the cell structure may contain
gallium arsenide, n-doped gallium arsenide, p-doped gallium
arsenide, aluminum gallium arsenide, n-doped aluminum gallium
arsenide, p-doped aluminum gallium arsenide, indium gallium
phosphide, alloys thereof, derivatives thereof, and combinations
thereof.
[0022] In some examples, the epitaxial material contains a gallium
arsenide buffer layer, an aluminum gallium arsenide passivation
layer, and a gallium arsenide active layer. In some examples, the
epitaxial material further has a second aluminum gallium arsenide
passivation layer. The gallium arsenide buffer layer may have a
thickness within a range from about 100 nm to about 500 nm, the
aluminum gallium arsenide passivation layers may each have a
thickness within a range from about 10 nm to about 50 nm, and the
gallium arsenide active layer may have a thickness within a range
from about 500 nm to about 2,000 nm. In other examples, the gallium
arsenide buffer layer may have a thickness of about 300 nm, each of
the aluminum gallium arsenide passivation layers may have a
thickness of about 30 nm, and the gallium arsenide active layer may
have a thickness of about 1,000 nm.
[0023] The sacrificial layer may contain aluminum arsenide, alloys
thereof, derivatives thereof, or combinations thereof. The
sacrificial layer may contain an aluminum arsenide layer, which may
have a thickness of about 20 nm or less, such as within a range
from about 1 nm to about 10 nm, preferably, from about 4 nm to
about 6 nm. In some embodiments, the sacrificial layers or material
may be exposed to a wet etch solution during an ELO etch step. The
wet etch solution may contain hydrofluoric acid, and further
contain a surfactant and/or a buffer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] So that the manner in which the above recited features of
the invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may be had
by reference to embodiments, some of which are illustrated in the
appended drawings. It is to be noted, however, that the appended
drawings illustrate only typical embodiments of this invention and
are therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0025] FIGS. 1A-1D depict a tiled growth substrate according to
embodiments described herein;
[0026] FIGS. 2A-2B depict another tiled growth substrate according
to embodiments described herein; and
[0027] FIGS. 3A-3B depict ELO thin film stacks disposed on a tiled
growth substrate according to embodiments described herein.
DETAILED DESCRIPTION
[0028] Embodiments of the invention generally relate to epitaxial
lift off (ELO) films and methods for producing such films.
Embodiments provide a method to simultaneously and separately grow
a plurality of ELO films or stacks on a common support substrate
which is tiled with numerous epitaxial growth substrates (e.g.,
epitaxial or crystalline substrates, wafers, or surfaces).
Thereafter, the ELO films are removed from the epitaxial growth
substrates by an etching step during an ELO process. The overall
throughput is quite high since multiple ELO films may be
manufactured while exposing each tiled growth substrate to the
numerous fabrication processes, similar to a bulk process. However,
multiple tiled growth substrates, each containing a plurality of
epitaxial growth substrates disposed on a support substrate, may be
exposed consecutively or simultaneously to the fabrication
processes. The tiled growth substrate containing the epitaxial
growth substrates disposed on the support substrate may be reused
to grow further ELO films.
[0029] FIGS. 1A-1D depict tiled growth substrate 100 containing a
plurality of epitaxial growth substrates 120 disposed on support
substrate 110, as described in one embodiment herein. In one
embodiment, epitaxial growth substrates 120 are epitaxial surfaces
on support substrate 110. The epitaxial surfaces may be a
substrate, wafer, thin film, layer, or other material which is
crystalline and is formed, deposited, grown, or otherwise attached
to support substrate 110. FIGS. 1A-1D illustrate tiled growth
substrate 100 containing twenty epitaxial growth substrates 120,
whereas rows of five epitaxial growth substrates 120 extend along
side 116 of support substrate 110 and rows of four epitaxial growth
substrates 120 extend along side 118 of support substrate 110.
[0030] FIGS. 2A-2B depict tiled growth substrate 200 containing a
plurality of epitaxial growth substrates 220 disposed on support
substrate 210, as described in another embodiment herein. In
another embodiment, as depicted in FIGS. 2A-2B, tiled growth
substrate 200 may contain sixteen epitaxial growth substrates 220,
whereas rows of four epitaxial growth substrates 220 extend along
side 216 of support substrate 210 and rows of four epitaxial growth
substrates 220 extend along side 218 of support substrate 210. In
other embodiments, tiled growth substrates 100 and 200 may contain
different amounts and placement configurations of epitaxial growth
substrates 120 or 220. Tiled growth substrates 100 and 200 each has
two or more epitaxial growth substrates 120 or 220, such as, for
examples, 3, 4, 5, 6, 9, 12, 16, 20, 24, 50, 100, or more epitaxial
growth substrates 120 or 220. In some embodiments, tiled growth
substrates 100 and 200 each may have any integer within a range
from 2 to 100, or more epitaxial growth substrates 120 or 220.
[0031] Support substrate 110 has lower surface 102 and upper
surface 104 and support substrate 210 has lower surface 202 and
upper surface 204. In one embodiment, adhesion layer 108 is
disposed on upper surface 104 of support substrate 110, and
epitaxial growth substrates 120 are disposed on adhesion layer 108
and adhesion layer 208 is disposed on upper surface 204 of support
substrate 210, and epitaxial growth substrates 220 are disposed on
adhesion layer 208.
[0032] Adhesion layers 108 as depicted in FIGS. 1A-1B and adhesion
layers 208 as depicted in FIG. 2A may be discontinuous layers
extending across upper surfaces 104 or 204, such that adhesion
layer 108 is disposed between epitaxial growth substrates 120 and
upper surface 104 and not extending outside of the area below
epitaxial growth substrates 120 or adhesion layer 208 is disposed
between epitaxial growth substrates 220 and upper surface 204 and
not extending outside of the area below epitaxial growth substrates
220. Alternatively, adhesion layer 108 depicted in FIGS. 1C-1D as
well as adhesion layer 208 depicted in FIG. 2B are shown as
continuous layers extending across upper surfaces 104 or 204.
[0033] In one embodiment, while forming tiled growth substrate 100,
adhesion layer 108 is discontinuously disposed on upper surface 104
of support substrate 110, and epitaxial growth substrates 120 are
disposed on adhesion layer 108 such that each epitaxial growth
substrate 120 completely covers each adhesion layer 108. Therefore,
each adhesion layer 108 has the same or less surface area as does
each epitaxial growth substrate 120 disposed thereover.
Alternatively, in another embodiment to form tiled growth substrate
100, an individual adhesion layer 108 is disposed on each epitaxial
growth substrate 120 so to partially or completely cover the
underside of each epitaxial growth substrate 120, and thereafter,
the epitaxial growth substrates 120 are positioned and attached to
the support substrate 110. The same configurations as described for
tiled growth substrate 100 are also for tiled growth substrate 200,
such as adhesion layer 208 is disposed on upper surface 204 of
support substrate 210 or adhesion layer 208 is disposed on each
epitaxial growth substrate 220 prior to positioning and attaching
the plurality of epitaxial growth substrates 220 on support
substrate 210.
[0034] In an alternative embodiment, adhesion layers 108 or 208 are
not present and epitaxial growth substrates 120 are disposed
directly on upper surface 104 of support substrate 110, or
epitaxial growth substrates 220 are disposed directly on upper
surface 204 of support substrate 210. Epitaxial growth substrates
120 or similar growth surfaces may be deposited, grown, or formed
directly on upper surface 104 of support substrate 110 by a
chemical vapor deposition (CVD) process, an atomic layer deposition
(ALD) process, an atomic layer epitaxy deposition (ALE) process, a
physical vapor deposition (PVD) or sputtering process, an
electroless deposition process. The CVD, ALD, and ALE processes
include thermal, plasma, pulsed, and metal-organic deposition
techniques.
[0035] The adhesion layer may be a single layer or contain multiple
layers. The adhesion layer may contain an adhesive or a glue and
may be a polymer, a copolymer, an oligomer, derivatives thereof, or
combinations thereof. In some embodiments, a single adhesion layer
or a plurality of adhesion layers may be disposed on the support
substrate and thereafter, epitaxial growth substrates are adhered
to the adhesion layer or each of the adhesion layers.
Alternatively, an adhesion layer may be disposed on each of the
epitaxial growth substrates and thereafter, the epitaxial growth
substrates are adhered to the support substrate.
[0036] In one embodiment, the adhesion layer contains a copolymer.
In one example, the copolymer may be an ethylene/vinylacetate (EVA)
copolymer or derivatives thereof. An EVA copolymer which is useful
as the adhesion layer is a WAFER GRIP adhesive film, commercially
available from Dynatex International, located in Santa Rosa, Calif.
In other examples, the adhesion layer may contain a hot-melt
adhesive, an organic material or organic coating, an inorganic
material, or combinations thereof. In some embodiments, the
adhesion layer may have a thickness within a range from about 5
.mu.m to about 100 .mu.m.
[0037] In another embodiment, the adhesion layer may contain an
elastomer, such as rubber, foam, or derivatives thereof.
Alternatively, the adhesion layer may contain a material such as
neoprene, latex, or derivatives thereof. The adhesion layer may
contain a monomer. For example, the adhesion layer may contain an
ethylene propylene diene monomer or derivatives thereof.
[0038] In other embodiments, the adhesion layer may contain or be
attached by a pressure sensitive adhesive (PSA), an acrylic PSA, or
other adhesive laminate. In one example, the PSA may be a 100 HT
(high temperature) acrylic PSA or a 100 HTL (high temperature
liner) acrylic PSA. In some examples, the adhesion layer may be a
PSA which is a laminate containing polyvinyl, polycarbonate,
polyester, derivatives thereof, or combinations thereof. In some
examples, the adhesion layer may contain a PSA laminate which has a
thickness within a range from about 50 .mu.m to about 250 .mu.m.
Many PSA laminates which may be used for the adhesion layer are
commercially available, such as acrylic PSA adhesive laminates (100
series) from 3M Inc., located in St. Paul, Minn.
[0039] In another embodiment, the adhesion layer may contain an
optical adhesive or an UV-curable adhesive when bonding or adhering
epitaxial growth substrates to the support substrate. Examples
provide that the optical or UV-curable adhesive contains butyl
octyl phthalate, tetrahydrofurfuryl methacrylate, acrylate monomer,
derivatives thereof, or combinations thereof. The curable adhesive
may be applied to the epitaxial growth substrates, to the support
substrate, or both. In some embodiments, a UV-light source may be
shined through epitaxial growth substrates in order to cure the
adhesive and form the adhesion layer. Generally, the adhesive may
be exposed to the UV radiation for a time period within a range
from about 1 minute to about 10 minutes, preferably, from about 3
minutes to about 7 minutes, such as about 5 minutes. The adhesive
may be cured at a temperature within a range from about 25.degree.
C. to about 75.degree. C., such as about 50.degree. C. The adhesion
layer may be formed from or contain an optical adhesive and/or a
UV-curable, such as commercially available as Norland UV-curable
optical adhesive.
[0040] In some examples, adhesion layers 108, 208, and 308 may
contain an optical adhesive or an ultraviolet-curable adhesive.
Adhesion layers 108, 208, and 308 may contain a mercapto ester
compound and may further contain butyl octyl phthalate,
tetrahydrofurfuryl methacrylate, acrylate monomer, derivatives
thereof, or combinations thereof. In other examples, adhesion
layers 108 and 208 may contain silicone or sodium silicate.
[0041] Regions, areas, spaces or spacings, such as gaps 112, extend
between epitaxial growth substrates 120 to separate each epitaxial
growth substrate 120 from each other on tiled growth substrate 100.
Gaps 112 may reveal upper surface 104 of support substrate 110, the
upper surface of adhesion layer 108, or the surface of other
materials, such as a stop layer, protective layer, or other layer.
Similarly for epitaxial growth substrates 220, regions, areas,
spaces or spacings, such as gaps 212 extend between epitaxial
growth substrates 220 to separate each epitaxial growth substrate
220 from each other. Gaps 212 may reveal upper surface 204 of
support substrate 210, the upper surface of adhesion layer 208, or
the surface of other materials, such as a stop layer, protective
layer, or other layer. Most examples provide that upper surface 104
of support substrate 110 is exposed within gaps 112 or upper
surface 204 of support substrate 210 is exposed within gaps
212.
[0042] In an alternative embodiment, not shown, tiled growth
substrate 100 or 200 may contain a plurality of epitaxial growth
substrates 120 or 220 disposed on support substrate 110 or 220
wherein the epitaxial growth substrates 120 or 220 are not
separated from each other. In some examples, tiled growth substrate
100 or 200 is a gallium arsenide substrate assembly containing a
plurality of epitaxial growth substrates 120 or 220 which contain
gallium arsenide or derivatives thereof.
[0043] Tiled growth substrate 100, 200, or 300 is a gallium
arsenide substrate assembly which has two or more gallium arsenide
growth substrates (e.g., epitaxial growth substrates 120, 220, or
320) disposed over the support substrates 110, 210, or 310. In many
embodiments described herein, the epitaxial growth substrates 120,
220, or 320 are gallium arsenide growth substrates.
[0044] Since gallium arsenide, such as a gallium arsenide growth
substrate, usually has a coefficient of thermal expansion (CTE)
within a range from about 5.73.times.10.sup.-6.degree. C..sup.-1 to
about 6.86.times.10.sup.-6.degree. C..sup.-1, the support substrate
is formed from or contains materials having a similar or
substantially similar CTE. In some embodiments described herein,
the support substrate, such as support substrates 110, 210, and/or
310, may be formed from or contain a material having a CTE of about
9.times.10.sup.-6.degree. C..sup.-1 or less, such as within a range
from about 5.times.10.sup.-6.degree. C..sup.-1 to about
9.times.10.sup.-6.degree. C..sup.-1, preferably, from about
5.2.times.10.sup.-6.degree. C..sup.-1 to about
8.5.times.10.sup.-6.degree. C..sup.-1, and more preferably, from
about 5.26.times.10.sup.-6.degree. C..sup.-1 to about
8.46.times.10.sup.-6.degree. C..sup.-1.
[0045] In many embodiments, the support substrate forms a maximum
strain of about 0.1% or less within the epitaxial growth
substrates, such as the gallium arsenide growth substrates while at
a temperature within a range from about 20.degree. C. to about
650.degree. C. In some examples, the support substrates (e.g.,
support substrates 110, 210, and/or 310) may have a CTE for
providing a maximum strain of about 0.1% or less within the
epitaxial growth substrates 120, 220, or 320 at a temperature of
about 650.degree. C., about 630.degree. C., or less. In some
examples, gaps 112 extend between and separate the epitaxial growth
substrates 120 from each other, as gaps 212 extend between and
separate the epitaxial growth substrates 220 from each other and
gaps 312 extend between and separate the epitaxial growth
substrates 320 from each other.
[0046] In order to achieve the same, similar, or substantially
similar coefficients of thermal expansion (CTEs) between the
epitaxial growth substrates and the support substrate, the types of
material in which the support substrate is chosen, in part, to
match or substantially match the CTE of the material contain within
the epitaxial growth substrates. Therefore, in many examples
described herein, the epitaxial growth substrates are wafers,
layers, thin films, or surfaces which contain epitaxial grown
gallium arsenide, crystalline gallium arsenide, gallium arsenide
alloys, or derivatives thereof.
[0047] The support substrates are utilized in tiled growth
substrates and may contain or be formed from a metallic material, a
ceramic material, a plastic material, or combinations thereof. The
support substrates generally contain or are made from at least one
metal or metallic material, ceramic material, or combinations
thereof. In some examples, the support substrates may be nonporous
or substantially nonporous. In other examples, the support
substrates may be resistant to hydrogen fluoride and hydrofluoric
acid.
[0048] In some embodiments, the support substrates may contain
niobium, niobium alloys, titanium carbide, magnesium silicate,
steatite, tungsten carbide, tungsten carbide cermet, iridium,
alumina, alumina ceramics, zirconium, zirconium alloys, zirconia,
zirconium carbide, osmium, tantalum, hafnium, molybdenum,
molybdenum alloys, oxides thereof, silicates thereof, alloys
thereof, derivatives thereof, or combinations thereof.
[0049] In some embodiments, the support substrate may contain or be
formed from at least one metallic material. The support substrate
may contain a single layer of the metallic material or multiple
layers of the same metallic material or different metallic
materials. In some examples, the metallic material of the support
substrate contains at least one metal such as titanium, zirconium,
hafnium, niobium, tantalum, chromium, molybdenum, tungsten,
manganese, rhenium, iron, ruthenium, cobalt, rhodium, nickel,
palladium, platinum, copper, silver, gold, zinc, aluminum, alloys
thereof, or combinations thereof. The metallic material may also
contain silicon, carbon, and/or boron, at various concentrations of
an alloy, and/or may contain other elements in trace amounts.
[0050] In some embodiments, the support substrate may contain or be
formed from at least one metallic material containing molybdenum or
molybdenum alloy. The molybdenum-containing metallic material may
contain annealed molybdenum, stress relieved condition molybdenum,
recrystallized molybdenum, annealed niobium, cold-worked niobium,
wrought niobium, annealed rhenium, deformed rhenium, annealed
tantalum, cold-worked tantalum, molybdenum disilicide (MoSi.sub.2),
molybdenum titanium carbon alloy (MoTiC alloy), molybdenum-titanium
alloy (95.5Mo-0.5Ti), molybdenum-titanium-carbon alloy
(Mo-0.5Ti-0.02C, molybdenum alloy 362),
molybdenum-titanium-zirconium alloy (MoTiZr alloy), molybdenum TZC
(Mo-1Ti-0.3Zr), arc cast molybdenum TZM (Mo-0.5Ti-0.1Zr; Mo-alloy
363) (stress relieved and recrystallized), P/M molybdenum TZM
(Mo-0.5Ti-0.1Zr; Mo-alloy 364) (stress relieved and
recrystallized), molybdenum rhenium alloy (Mo-44.5Re--annealed);
molybdenum rhenium alloy (Mo-47.5Re--annealed and deformed), Mo--Cu
composites (Ametek molybdenum-copper composites AMC 7525, 8020, or
8515), derivatives thereof, alloys thereof, or combinations
thereof. In some examples, the support substrate may contain or be
formed from molybdenum-copper containing by weight about 75%
molybdenum and about 25% copper, or about 80% molybdenum and about
20% copper, or about 85% molybdenum and about 15% copper.
[0051] In some embodiments, the support substrate may contain or be
formed from at least one metallic material containing tungsten or
tungsten alloy. The tungsten-containing metallic material may
contain high density machinable tungsten (CMW.RTM. 1000 AMS-T-21014
AMS-7725 ASTM B777), tungsten alloys (CMW.RTM. 3000
alloy--AMS-T-21014 AMS-7725 and CMW.RTM. 3950--alloy AMS-T-21014
ASTM B777), and W--Cu composites (Ametek tungsten-copper composites
AWC 8515, 8812, or 9010), derivatives thereof, alloys thereof, or
combinations thereof. In some examples, the support substrate may
contain or be formed from tungsten-copper composites containing by
weight about 85% tungsten and about 15% copper, or about 88%
tungsten and about 12% copper, or about 90% tungsten and about 10%
copper.
[0052] In other embodiments, the support substrate may contain or
be formed from at least one metallic material containing niobium or
niobium alloy. The niobium-containing metallic material may contain
niobium alloy C-103 (89Nb-10Hf-1Ti) (cold-rolled, stress relieved,
and recrystallized), niobium alloy C-129Y (80Nb-10W-10Hf-0.1Y),
niobium alloy Cb-752 (Nb-10W-2.5Zr), derivatives thereof, alloys
thereof, or combinations thereof.
[0053] In other embodiments, the support substrate may contain or
be formed from at least one metallic material containing titanium
or titanium alloy and/or zirconium or zirconium alloy. The metallic
material containing titanium or zirconium may contain titanium
alloy Ti-6Al-2Sn-4Zr-2Mo-0.1Si (duplex annealed), titanium
Ti-6Al-2Sn-4Zr-2Mo (Ti-6-2-4-2) (duplex annealed and sheet),
zirconium (grade 702--commercially pure), zirconium (reactor
grade), derivatives thereof, alloys thereof, or combinations
thereof.
[0054] In other embodiments, the support substrate may contain or
be formed from at least one controlled expansion (CE) alloy, such
as an aluminum-silicon alloy. In one example, the aluminum-silicon
alloy contains by weight about 30% aluminum and about 70% silicon,
such as the CE7 Al--Si controlled expansion alloy, available from
Osprey Metals.
[0055] In other embodiments, the support substrate may contain or
be formed from at least one metallic material containing iron or
iron alloy. The iron-containing metallic material may contain an
iron-nickel alloy, an iron-nickel-manganese alloy
(Fe-36Ni-0.35Mn-0.20Si-0.02C) Carpenter Invar 36.RTM. alloy (cold
drawn bars, cold rolled strips, and annealed bars & strips), an
iron-nickel-cobalt alloy, Carpenter Kovar.RTM. alloy (glass and
ceramic sealing alloy), iron-nickel-cobalt-titanium alloy,
iron-nickel-cobalt-titanium-niobium alloy,
iron-nickel-cobalt-titanium-tantalum alloy,
iron-nickel-cobalt-titanium-niobium-tantalum alloy Carpenter
Pyromet.RTM. CTX-3 Superalloy (heat treated and heat treatment for
brazing cycles over 982.degree. C.), an
iron-nickel-cobalt-niobium-titanium-aluminum alloy, INCOLOY.RTM.
alloy 903, an iron-nickel-cobalt-niobium-titanium alloy,
INCOLOY.RTM. alloy 907, an iron-nickel-cobalt-niobium-titanium
alloy, INCOLOY.RTM. alloy 909, Fe--Ni alloys, Fe--Ni--Mn alloys
(Allegheny Ludlum AL 42.TM. electrical alloy), UNS K94100,
derivatives thereof, alloys thereof, or combinations thereof.
[0056] In one example, the support substrate may contain or be
formed from an iron-nickel-manganese alloy which contains by weight
about 58.4% of Fe, about 40.8% of Ni, and about 0.5% of Mn, is the
AL 42.TM. electrical alloy, available from Allegheny Ludlum
Corporation, USA.
[0057] In another example, the support substrate may contain or be
formed from an iron-nickel-manganese alloy which contains by weight
about 63.4% of Fe, about 36% of Ni, about 0.35% of Mn, about 0.20%
of Si, and about 0.02% of C, is Carpenter Invar 36.RTM. alloy,
available as cold drawn bars, cold rolled strips, and annealed bars
and strips.
[0058] In another example, the support substrate may contain or be
formed from an iron-nickel-cobalt alloy which contains by weight
about 53.4% of Fe, about 29% of Ni, about 17% of Co, about 0.30% of
Mn, about 0.20% of Si, and about 0.02% of C, is Carpenter
Kovar.RTM. Fe--Ni--Co alloy.
[0059] In another example, the support substrate may contain or be
formed from an iron-nickel-cobalt-titanium alloy may contain
niobium, tantalum, or both niobium and tantalum. The
iron-nickel-cobalt-titanium alloy contains by weight about 37%-39%
of Ni, about 13%-15% of Co, about 1.25%-1.75% of Ti, and about
4.50%-5.50% of Nb and Ta mixture, and about 36.3%-41.8% or balance
of Fe, is Carpenter Pyromet.RTM. CTX-3 superalloy.
[0060] In another example, the support substrate may contain or be
formed from an iron-nickel-cobalt-niobium-titanium-aluminum alloy
which contains by weight about 36%-40% of Ni, about 13%-17% of Co,
about 0.30%-1.15% of Al, about 1.00%-1.85% of Ti, about 2.40%-3.50%
of Nb, and about 36.5%-47.3% or balance of Fe, is INCOLOY.RTM.
alloy 903.
[0061] In another example, the support substrate may contain or be
formed from an iron-nickel-cobalt-niobium-titanium alloy which
contains by weight about 35%-40% of Ni, about 12%-16% of Co, about
4.30%-5.20% of Nb, about 1.3%-1.8% of Ti, about 0.02%-0.20% of Al,
about 0.07%-0.35% of Si, and about 36.5%-47.3% or balance of Fe, is
INCOLOY.RTM. alloy 907.
[0062] In another example, the support substrate may contain or be
formed from an iron-nickel-cobalt-niobium-titanium alloy which
contains by weight about 35%-40% of Ni, about 12%-16% of Co, about
4.30%-5.20% of Nb, about 1.3%-1.8% of Ti, about 0.001%-0.15% of Al,
about 0.25%-0.50% of Si, about 0.001%-0.06% of C, and about
36.3%-47.1% or balance of Fe, is INCOLOY.RTM. alloy 909.
[0063] In some embodiments, the support substrate may contain or be
formed from at least one ceramic material. The support substrate
may contain a single layer of the ceramic material or multiple
layers of the same ceramic material or different ceramic materials.
The ceramic material of the support substrate contains at least one
material such as aluminum oxide, alumina, silicon oxide, silica,
zirconium oxide, zirconia, hafnium oxide, hafnia, magnesium oxide,
magnesium silicon oxide (steatite), magnesium scandium sulfide,
cerium boride, calcium boride, iron aluminum oxide, ferro aluminum
oxide, graphite, oxides thereof, borides thereof, derivatives
thereof, or combinations thereof.
[0064] In some specific examples, the support substrate may contain
or be formed from at least one ceramic material selected from 96%
alumina, thick-film (as fired), 92% alumina (opaque), 85% alumina
(vitreous body), 95% alumina (vitreous body), 99.5% alumina
(vitreous body), alumina (96% Al.sub.2O.sub.3), 99.5% alumina (thin
film substrate), 99.6% alumina (thin-film substrate), beryllia
(99.5% BeO), calcium boride, cerium boride (CeB.sub.6), albite
(Feldspar NaAlSi.sub.3O.sub.8), calcite (CaCO.sub.3), steatite
(magnesium silicon oxide), magnesium scandium sulfide
(MgSc.sub.2S.sub.4), zinc gallium sulfide (ZnGa.sub.2S.sub.4),
CoorsTek alumina AD-85 (nom. 85% Al.sub.2O.sub.3), CoorsTek alumina
AD-90 (nom. 90% Al.sub.2O.sub.3), CoorsTek alumina AD-94 (nom. 94%
Al.sub.2O.sub.3), CoorsTek alumina AD-96 (nom. 96%
Al.sub.2O.sub.3), CoorsTek alumina FG-995 (nom. 98.5%
Al.sub.2O.sub.3), CoorsTek alumina AD-995 (nom. 99.5%
Al.sub.2O.sub.3), CoorsTek alumina AD-998 (nom. 99.8%
Al.sub.2O.sub.3), Advanced Ceramics ALC 1081 (C-786) alumina,
Advanced Ceramics ALC 1082 (C-786) alumina, Advanced Ceramics ACL
1085 (C-795) alumina, CeramTec 665 steatite (MgO--SiO.sub.2),
CeramTec 771 94% alumina (Al.sub.2O.sub.3), CeramTec Grade 614
White 96% alumina (Al.sub.2O.sub.3), CeramTec Grade 698 Pink 96%
alumina (Al.sub.2O.sub.3), CeramTec 975 99.5% alumina
(Al.sub.2O.sub.3), CeramTec 433 99.9% alumina (Al.sub.2O.sub.3),
CeramTec 950 toughened alumina (Al.sub.2O.sub.3--ZrO.sub.2),
CeramTec 848 zirconia (ZrO.sub.2), Corning 7056 alkali borosilicate
crushed/powdered glass, Du--Co ceramics DC-9-L-3 steatite, Du--Co
Ceramics DC-10-L-3 steatite, Du--Co ceramics DC-16-L-3 steatite,
Du--Co Ceramics CS-144-L-5 steatite, Du--Co ceramics DC-265-L-6
alumina (96% Al.sub.2O.sub.3), ferro aluminum oxide P87, P890,
P3640, or P3142, ICE Al.sub.2O.sub.3 94, 96, 99.5, or 99.8, ICE Hot
Pressed SiC, ICE Mullite (3Al.sub.2O.sub.3--SiO.sub.2), ICE
Steatite L-4 or L-5, CoorsTek Mullite (S2), 3M Nextel.TM. 440, 550,
610, 650, or 720 Industrial Ceramic Fiber, Morgan Advanced Ceramics
Deranox.TM. 970 or 975 alumina, Morgan Advanced Ceramics Sintox.TM.
FF alumina, Saxonburg Ceramics L-3 or L-5 Steatite, alumina
(Saxonburg Ceramics S-697/S-700-02 alumina), alumina (Saxonburg
Ceramics S-700-22 alumina), alumina (Saxonburg Ceramics S-660
alumina), alumina (Saxonburg Ceramics S-699 alumina (crushable),
CoorsTek Zirconia-Toughened alumina (ZTA), graphite (Poco Graphite
Fabmate.RTM. Pore-Free Specialty Graphite and Poco Graphite
Durabraze.RTM. purified/machined specialty graphite), Wieland
ALLUX.RTM./ZIROX.RTM. ceramic veneering, oxides thereof, borides
thereof, derivatives thereof, or combinations thereof.
[0065] In other embodiments described herein, a method for forming
a tiled growth substrate is provided which includes forming a
plurality of epitaxial growth substrates, films, or materials
during ELO processes, and thereafter, adhering the plurality of
epitaxial growth substrates on a support substrate. Subsequently,
the method provides using the tiled growth substrate to form
additional ELO films or other epitaxial materials by depositing a
sacrificial layer over each epitaxial growth substrate disposed on
the support substrate and depositing epitaxial materials over each
of the sacrificial layers. The epitaxial materials may contain a
single layer, but usually contains a plurality of layers, such as a
photovoltaic or solar device or portion thereof. The method further
provides etching the sacrificial layers while removing the
epitaxial materials from the epitaxial growth substrates during an
additional ELO process.
[0066] In one example, a method for forming a tiled growth
substrate is provided which includes forming a first sacrificial
layer on a host substrate, forming a first epitaxial layer over the
first sacrificial layer, etching the first sacrificial layer while
removing the first epitaxial layer from the host substrate and
forming a first epitaxial growth substrate during a first ELO
process, forming a second sacrificial layer on the host substrate,
forming a second epitaxial layer over the second sacrificial layer,
etching the second sacrificial layer while removing the second
epitaxial layer from the host substrate and forming a second
epitaxial growth substrate during a second ELO process, and
adhering the first and second epitaxial growth substrates on a
support substrate.
[0067] In another example, a method for forming a tiled growth
substrate is provided which includes forming a first epitaxial
layer on a first sacrificial layer disposed on a host substrate,
etching the first sacrificial layer while removing the first
epitaxial layer from the host substrate to form a first epitaxial
growth substrate during a first ELO process. The method further
provides forming a plurality of epitaxial growth substrates during
multiple deposition and ELO processes. Subsequently, the method
provides adhering the plurality of epitaxial growth substrates on a
support substrate to form the tiled growth substrate. In another
embodiment, the method provides exposing the tiled growth
substrate, that is, the epitaxial growth substrate disposed on the
support substrate, to additional deposition and ELO processes in
order to form a variety of ELO films and materials.
[0068] FIG. 3A illustrates tiled growth substrate 300 containing a
plurality of epitaxial growth substrates 320 disposed on adhesion
layer 308, which is further disposed on support substrate 310, as
described in one embodiment herein. In other embodiments, support
substrate 310 contains a plurality of epitaxial growth substrates
320 each independently disposed on a separate adhesion layer 308,
such that a plurality of adhesion layers 308 extends support
substrate 310. In other embodiments, a plurality of epitaxial
growth substrates 320 is directly disposed on support substrate 310
without an adhesion layer.
[0069] Tiled growth substrate 300 may contain a single row or
multiple rows of epitaxial growth substrates 320. A row containing
five epitaxial growth substrates 320 is illustrated in FIG. 3A. In
one example, tiled growth substrate 300 contains four rows,
therefore has twenty epitaxial growth substrates 320. Tiled growth
substrate 300 is depicted containing a plurality of epitaxial
stacks 420 disposed thereon, such that there is an epitaxial stack
420 formed or deposited on each epitaxial growth substrate 320, as
described by embodiments herein. A space, area, or region, such as
gap 312, extends between each of the ELO film stacks 316 including
each epitaxial stack 420 disposed on an independent epitaxial
growth substrate 320.
[0070] FIG. 3B depicts a single ELO film stack 316 containing
epitaxial stack 420 disposed on an epitaxial growth substrate 320,
according to embodiments described herein. Adhesion layer 308 and
support substrate 310 were not shown in order to illustrate details
of ELO film stack 316. In one embodiment, epitaxial stack 420
contains epitaxial material 418 disposed on sacrificial layer 404,
which is disposed on epitaxial growth substrate 320. Epitaxial
material 418 may contain at least gallium arsenide active layer 410
of gallium arsenide, but may contain a plurality of other layers,
including buffer and passivation layers. As depicted in FIGS.
3A-3B, epitaxial material 418 disposed on sacrificial layer 404,
and epitaxial material 418 contains buffer layer 406 disposed on
sacrificial layer 404, passivation layer 408 disposed on buffer
layer 406, gallium arsenide active layer 410 disposed on
passivation layer 408, and passivation layer 412 disposed on
gallium arsenide active layer 410, as described in embodiments
herein.
[0071] While FIG. 3A depicts a single row of five epitaxial stacks
420 disposed on tiled growth substrate 300, epitaxial stacks 420
may be disposed on tiled growth substrate 300 in a variety of
configurations. A single row or multiple rows of epitaxial stacks
420 may be disposed on tiled growth substrate 300. Each row of five
epitaxial stacks 420 may have two or more epitaxial stacks 420. In
some examples, tiled growth substrate 300 may contain two, three,
four, five six, ten, twelve, twenty, twenty four, thirty, fifty,
one hundred, or more epitaxial stacks 420, each contained on an
epitaxial growth substrate 320. In various embodiments, the ELO
process includes removing sacrificial layers 404 during an etching
process, while peeling the ELO film or epitaxial material 418 from
epitaxial growth substrates 320 or other layer of epitaxial
material 418 and forming an etch crevice therebetween until
epitaxial material 418 is removed from epitaxial growth substrate
320.
[0072] In one embodiment, thin film stacks on tiled growth
substrate 300 is provided which includes a plurality of epitaxial
stacks 420, each disposed on epitaxial growth substrates 320 (e.g.,
containing GaAs), wherein each epitaxial stack 420 contains a layer
of epitaxial material 418 deposited over a layer of sacrificial
material 404, as depicted in FIGS. 3A-3B.
[0073] The layers of epitaxial material 418 and/or sacrificial
material 404 within each epitaxial stack 420 may have the same
composition or different compositions. In some examples, each layer
of the epitaxial material 418 may independently contain gallium
arsenide, aluminum gallium arsenide, indium gallium phosphide,
alloys thereof, derivatives thereof, or combinations thereof. Also,
each layer of the epitaxial material 418 may have multiple layers.
In one example, each layer of the epitaxial material 418
independently has a layer containing gallium arsenide and another
layer containing aluminum gallium arsenide. In other examples, each
layer of the epitaxial material 418 may independently contain
buffer layer 406, passivation layer 408, and gallium arsenide
active layer 410. In some examples, each layer of the epitaxial
material 418 further contains a second passivation layer 412. In
one example, each layer of the epitaxial material 418 may
independently have buffer layer 406 containing gallium arsenide,
passivation layers 408 and 412 containing aluminum gallium
arsenide, and gallium arsenide active layer 410.
[0074] In some examples, the gallium arsenide buffer layer may have
a thickness within a range from about 100 nm to about 400 nm, each
of the passivation layers 408 and 412 may have a thickness within a
range from about 10 nm to about 50 nm, and the gallium arsenide
active layer 410 may have a thickness within a range from about 400
nm to about 2,000 nm. In other examples, the gallium arsenide
buffer layer 406 may have a thickness of about 300 nm, each of the
passivation layers 408 and 412 may have a thickness of about 30 nm,
and the gallium arsenide active layer 410 may have a thickness of
about 1,000 nm. Each of the passivation layers 408 and 412 may
independently contain aluminum gallium arsenide alloy or a
derivative thereof.
[0075] In other examples, each layer of the gallium arsenide active
layer 410 or the epitaxial material 418 may have a photovoltaic
cell structure containing multiple layers. In one example, the
photovoltaic cell structure may contain gallium arsenide, n-doped
gallium arsenide, p-doped gallium arsenide, aluminum gallium
arsenide, n-doped aluminum gallium arsenide, p-doped aluminum
gallium arsenide, indium gallium phosphide, alloys thereof,
derivatives thereof, or combinations thereof.
[0076] In another embodiment, each layer of the sacrificial
material 404 may independently contain a material such as aluminum
arsenide, alloys thereof, derivatives thereof, or combinations
thereof. In some examples, each layer of the sacrificial material
404 may independently contain an aluminum arsenide layer having a
thickness of about 20 nm or less, such as within a range from about
1 nm to about 10 nm, preferably, from about 4 nm to about 6 nm.
[0077] Epitaxial growth substrates 320 may contain or be formed of
a variety of materials, such as Group III/IV materials, and may be
doped with other elements. In one embodiment, epitaxial growth
substrates 320 contain gallium arsenide, gallium arsenide alloys,
or derivatives thereof. In some example, epitaxial growth
substrates 320 may contain n-doped gallium arsenide or p-doped
gallium arsenide. Gallium arsenide, such as a gallium arsenide
growth substrate, may have a CTE within a range from about
5.73.times.10.sup.-6.degree. C..sup.-1 to about
6.86.times.10.sup.-6.degree. C..sup.-1.
[0078] In another embodiment, a method for forming various
epitaxial materials on tiled growth substrate 300 is provided which
includes depositing a plurality of epitaxial stacks 420 on
epitaxial growth substrates 320, wherein each ELO stack 316
contains epitaxial stack 420 containing a layer of epitaxial
material 418 and each epitaxial stack 420 is deposited over a layer
of sacrificial material 404.
[0079] In another embodiment, a method for forming various
epitaxial materials on tiled growth substrate 300 is provided which
includes depositing a plurality of epitaxial stacks 420 on
epitaxial growth substrates 320, wherein each epitaxial stack 420
contains a layer of epitaxial material 418 deposited over a layer
of sacrificial material 404, and etching the layers of sacrificial
material 404 while removing the layers of epitaxial material 418
from tiled growth substrate 300 during at least one ELO
process.
[0080] In some embodiments, tiled growth substrate 300 may have 2,
3, 4, 5, 6, 10, 12, 20, 24, 50, 100, or more epitaxial stacks. Each
layer of the epitaxial material 418 may have the same composition
or different compositions. Similarly, each layer of the sacrificial
material 404 may have the same composition or different
compositions. Each layer of the epitaxial material 418 may contain
multiple layers and may independently contain gallium arsenide,
aluminum gallium arsenide, or derivatives thereof. Examples provide
that each layer of the epitaxial material 418 may independently
have a layer containing gallium arsenide and another layer
containing aluminum gallium arsenide. In one embodiment, each layer
of the epitaxial material 418 may independently contain buffer
layer 406, passivation layer 408, gallium arsenide active layer
410, and passivation layer 412. In some examples, buffer layer 406
contains gallium arsenide, passivation layers 408 and 412 may each
independently contain aluminum gallium arsenide, and active layer
410 may contain gallium arsenide.
[0081] In some embodiments, sacrificial layers 404 or material may
be exposed to a wet etch solution during an ELO etch step. The wet
etch solution may contain hydrofluoric acid, and further contain a
surfactant and/or a buffer. In some example, sacrificial layers 404
or material may be etched during a wet etch process at a rate of
about 0.3 mm/hr or greater, preferably, about 1 mm/hr or greater,
and more preferably, about 5 mm/hr or greater.
[0082] In some alternative embodiments, sacrificial layers 404 or
material may be exposed to an electrochemical etch during an ELO
etch step. The electrochemical etch may include a biased process or
a galvanic process. In another example, sacrificial layers 404 or
material may be exposed to a vapor phase etch during an ELO etch
step. The vapor phase etch includes exposing sacrificial layers 404
or material to hydrogen fluoride vapor. The ELO process as
described herein may contain an etching process or an etching step
such as a photochemical etch process, a thermally enhanced etch
process, a plasma enhanced etch process, a stress enhanced etch
process, derivatives thereof, or combinations thereof.
[0083] In another embodiment, a method for forming multiple
epitaxial thin films during an epitaxial lift off process is
provided which includes depositing a plurality of aluminum arsenide
sacrificial layers simultaneously on a plurality of gallium
arsenide growth surfaces disposed on a support substrate, wherein a
single aluminum arsenide sacrificial layer is deposited on each
gallium arsenide growth surface, and each of the gallium arsenide
growth surfaces is separately disposed on the support substrate,
next to each other, and a gap extends between and separates the
gallium arsenide growth surfaces from each other.
[0084] The method further includes depositing a plurality of buffer
layers simultaneously on the plurality of aluminum arsenide
sacrificial layers. A single buffer layer may be deposited by CVD
on each aluminum arsenide sacrificial layer. Subsequently, a
plurality of gallium arsenide active layers are simultaneously
grown or otherwise deposited on the plurality of buffer layers,
wherein a single gallium arsenide active layer is deposited on each
buffer layer.
[0085] A support film, handle, or tape may be disposed on or over
the opposite side of the gallium arsenide active layers or the ELO
film as the support substrate. The support film is used to
stabilize the gallium arsenide active layers by maintaining
compression and to hold the gallium arsenide active layers during
the etching and removal steps of the ELO process, and thereafter.
The ELO process includes etching the aluminum arsenide sacrificial
layers while separating the gallium arsenide active layers from the
gallium arsenide growth surfaces. During the etching process, the
support film may be used to provide leverage and separate the ELO
films from the epitaxial growth substrates row by row or all of the
rows at the same time.
[0086] While the foregoing is directed to embodiments of the
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
* * * * *